 Historically, the Chicago Skyway was signed as, and was widely considered to be part of, I-90 from the mid-1960s forward (after I-90 in this area had been swapped with I-94).However, around 1999, the City of Chicago realized they had never received official approval to designate the Skyway as I-90.The city subsequently replaced most of the "I-90" signage with "TO I-90/I-94" signage.